1. Technical Field
The present invention relates to a control apparatus for turning off a computer system, and more particularly to a control apparatus for turning off power supplied to a computer system having a display, where power supplied to the display is turned off first and power supplied to the entire computer system is turned off last. The present invention also relates to methods for turning off power supplied to a computer system having a display, where power supplied to the display is turned off first and power supplied to the entire computer system is turned off last.
2. Related Art
Utilizing a conventional technique to turn off a computer system having a display screen, the computer system is turned off when a user presses a power switch and cuts off power directly to a switching mode power supply. As a result, power is cut off abruptly to the entire computer system, including the display screen. In addition, conventionally power is supplied simultaneously to all units in a single apparatus and power is disconnected simultaneously from all units in a single apparatus.
Using the conventional technique described above to turn off a computer system, the display screen can be damaged by an electrical surge when power to the entire system and to the display is simultaneously and abruptly turned off. Also, the display screen experiences flicker and afterimage when power to the entire system and the display are turned off simultaneously. Malfunctions in the display may occur due to rush current and abnormal voltages.
There do exist power supply control systems which control various aspects of power supplies. For example, some power supply control systems are disclosed in U.S. Pat. No. 4,747,041 for Automatic Power Control System Which Automatically Activates and Deactivates Power to Selected Peripheral Devices Based Upon System Requirement issued to Engel et al., U.S. Pat. No. 4,204,249 for Data Processing System Power Control issued to Dye et al., U.S. Pat. No. 5,414,863 for Power Control Staggering Circuit for Powering Different Components at Different Delay Timings issued to Lee et al., and U.S. Pat. No. 5,535,400 for SCSI Disk Drive Power Down Apparatus issued to Belmont.
Some examples of power supply control systems partially controlling power supplied to display screens are disclosed in U.S. Pat. No. 5,389,952 for Low-Power-Consumption Monitor Standby System issued to Kikinis, U.S. Pat. No. 5,008,846 for Power and Signal Supply Control Device issued to Inoue, U.S. Pat. No. 5,511,201 for Data Processing Apparatus, Power Supply Controller and Display Unit issued to Kamimaki et al., U.S. Pat. No. 5,481,732 for CRT Monitor Power Control Unit issued to Shahbazi, U.S. Pat. No. 5,703,629 for Computer System Including Protected Graphics Display Control Signal Sequencing issued to Mermelstein et al., and U.S. Pat. No. 5,463,408 for Liquid-Crystal Display issued to Mio.
Currently there are some power supply control systems which claim to offer protection to displays under certain conditions. However, I have discovered that it would be desirable to develop an enhanced power supply control system to control power supplied to a display in order to better protect against damage to the display.